There is a type of vehicle provided with such a rotational vibration attenuating device (dynamic vibration absorber) as described in Japan Laid-open Patent Application Publication No. 2017-524109 on a power transmission path so as to attenuate rotational vibration occurring due to fluctuation in torque from an engine or so forth.
The rotational vibration attenuating device, described in Japan Laid-open Patent Application Publication No. 2017-524109, includes a carrier to which power is inputted, an absorber mass (inertia member) rotatable relative to the carrier, and a plurality of absorber springs (elastic members). The plural absorber springs are elastic members elastically coupling the carrier and the absorber mass in a rotational direction. The plural absorber springs are composed of a plurality of pairs of flat springs disposed in opposition. Additionally, a plurality of sliders are provided such that each is interposed between each pair of flat springs.
In this device, the sliders are radially moved by centrifugal forces, whereby fulcrums in elastic deformation of the flat springs are shifted. In other words, the flat springs are changed in bending stiffness. Because of this, torsional stiffness for attenuating rotational vibration (i.e., torsional characteristics or vibration attenuating characteristics) is changed in accordance with rotational speed.
In the device described in Japan Laid-open Patent Application Publication No. 2017-524109, the torsional stiffness of the device can be changed in accordance with the centrifugal forces (i.e., rotational speed).
Now, there has been proposed a vehicle equipped with a cylinder deactivation system as a type of engine installed vehicle. In the cylinder deactivation system, part or entirety of cylinders are deactivated in low load operation or idling operation. It is desirable for the vehicle equipped with the cylinder deactivation system herein described to meet a demand of making characteristics for attenuating rotational vibration changeable in accordance with change in number of cylinders to be activated.
However, the device described in Japan Laid-open Patent Application Publication No. 2017-524109 cannot cope with the demand described above. Additionally, it is difficult to accurately regulate relation between change in stiffness of each flat spring caused by shifting of the fulcrum thereof and displacement of each slider moved by a centrifugal force.